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Abstract. The role of Juvenile Hormone (JH) during reproductive development and diapause was investigated in the boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae). JH sythesized by corpora allata (CA) in vitro of A.grandis was identified as JH‐UJ by high‐performance liquid chromatography and by conversion to the methoxyhydrin. Optimal conditions for the use of a short‐term assay in vitro were established to examine profiles of CA activity. In addition, rates of JH degradation by JH‐specific esterase were determined. Patterns of CA and JH‐esterase activity during reproductive development and the diapause state were established with laboratory‐reared reproductive weevils and diapausing weevils collected as larvae and pupae in the field after the cotton‐growing season. The results indicate that JH production is elevated in reproductive females whereas males and winter field‐collected females show no CA activity. Vitellogenin concentrations in haemolymph and rates of oviposition were studied in relation to CA activity and JH degradation. An attempt to induce diapause in the laboratory failed.

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